He has been under pressure since his Nov. 15 broadcast, when he called the former Alaska governor a "world-class idiot" and suggested she receive the same disgusting treatment given to slaves as described in a slaveholder's diary.

Bashir was responding to Palin's comparison of America's debt to China to slavery.

Bashir's original statement was made on a Friday, and he issued an apology the following Monday, on Nov. 18. But criticism continued, especially after fellow MSNBC host Alec Baldwin was suspended, then fired, after using an anti-gay slur against photographers who approached his wife and baby.

Critics, including Baldwin himself, noted that Bashir made his statement on the air and clearly was reading from a prepared script, not off-the-cuff and in anger on a public street, as Baldwin had done.

In his apology, Bashir said he requested time off near Thanksgiving. He was still off the air this week, and an MSNBC spokesman said Monday he was "on vacation."

"Martin Bashir resigned today, effective immediately," MSNBC President Phil Griffin told Politico Wednesday. "I understand his decision and I thank him for three great years with MSNBC. Martin is a good man and respected colleague. We wish him only the best."

Bashir said in his own statement:

After making an on-air apology, I asked for permission to take some additional time out around the Thanksgiving holiday.

Upon further reflection, and after meeting with the president of MSNBC, I have tendered my resignation. It is my sincere hope that all of my colleagues, at this special network, will be allowed to focus on the issues that matter without the distraction of myself or my ill-judged comments.

I deeply regret what was said, will endeavor to work hard at making constructive contributions in the future and will always have a deep appreciation for our viewers, who are the smartest, most compassionate and discerning of all television audiences.

I would also wish to express deepest gratitude to my immediate colleagues, and our contributors, all of whom have given so much of themselves to our broadcast.